How to find the lost InnoDB engine

The night of the master from copying, conveniently adjusted down from the library of the MY.CNF. The morning remembered from the library forgot to restart, after the command then opened slave, incredibly error

last_sql_errno:1286
Last_sql_error:error executing row event: ' Unknown storage engine ' InnoDB '

Strange, how can the error not know the storage engine InnoDB. To view the next engine:

Mysql> show engines; +--------------------+---------+-----------------------------------------------------------+--------------+---- --+------------+
| Engine | Support | Comment | Transactions | XA |
savepoints | +--------------------+---------+-----------------------------------------------------------+--------------+---- --+------------+
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO | | Performance_schema | YES | Performance Schema | NO | NO | NO | | MyISAM | DEFAULT | MyISAM Storage Engine | NO | NO | NO | | CSV | YES | CSV Storage Engine | NO | NO | NO | | Mrg_myisam | YES |         Collection of identical MyISAM tables            | NO | NO |
NO | +--------------------+---------+-----------------------------------------------------------+--------------+---- --+------------+ 5 rows in Set (0.01 sec)

No, InnoDB is really gone. My heart panic, never heard of the engine will disappear! Let's see what the error log says.

130829  8:42:30 [note] Slave I/O thread:connected to master ' slave@192.168.0.153:3306 ', replication started in log ' Mys  ql-bin.000023 ' at position 232546566
130829  8:42:30 [ERROR] Slave sql:error-Executing row event: ' Unknown storage Engine ' InnoDB ', error_code:1286
130829  8:42:30 [Warning] slave:unknown storage engine ' InnoDB ' error_code:12
130829  8:42:30 [ERROR] Error running query, slave SQL thread aborted. Fix the problem, and restart the slave SQL thread with "Slave START". We stopped at log ' mysql-bin.000023 ' position 225856952

Looks like InnoDB really disappeared.

You have to rely on yourself before you can improve yourself. Think about the process of the event: InnoDB disappeared. Why would it disappear? Why is it disappearing today? What have I ever done? Think about it.

Configuration file, yes, I adjusted the my.cnf at night and then restarted MySQL in the morning, then InnoDB disappeared. OK, the reason has been found. Quickly will adjust before and after the configuration file contrast, see what we have changed Ah, found the most suspicious of a configuration item:

Innodb_log_files_in_group = 3

Change back to the value before the adjustment of 2, restart MySQL, open slave, copy normal, look at the engine, InnoDB also back! Lucky. InnoDB's disappearance is due to the fact that modifying the configuration causes MySQL to generate a new ib_logfile log with the old ib_logfile log confusion. To organize the steps to modify this configuration item

Service mysqld Stop
CD to the data directory under
MV ib_logfile* to other directories
modify Innodb_log_files_in_group
service mysqld start